Some characteristics of the histological structure of the fetal bovine pancreas

Some properties of histological structure of fetal bovine pancreas were demonstrated using light microscopic methods. The different forms of acino-insular complexes were described: 1) acino-insular complexes with single B-cells including epithelial layer of acini; 2) acino-insular complexes with segmental (sector) localization of insular cell groups; 3) acino-insular complexes with small and more large groups of endocrine cells timely contacted with acini; 4) acino-insular complexes at the stage of separation of endocrine cell groups (microislets) from acini. The consideration of acino-insular complexes in morphogenesis of bovine endocrine pancreas in discussed.     

Detection of lipopeptide complexes in lipid fractions of Proteus mirabilis

Covalently bonded complexes of phospholipids with peptides were detected in the lipid fractions of Proteus mirabilis. The lipopeptides were developed with ninhydrin after treating thin-layer chromatograms with H1 or 0.1 N HCl at 100 degrees C for 4 hours. The complexes can be chromatographed in silicic acid unfixed layers using neutral or weakly acidic systems of solvents. The complexes break down in layers fixed with gypsum or treated with diluted alkali solutions. The complexes can contain several phospholipid molecules which make them soluble in organic solvents. The lowest proportion between phospholipids and peptide components was 4:1. Apparently, the complexes contain O-ester and pyrophosphoric bonds.     

Stereoselective aldol addition reactions of Fischer carbene complexes via electronic tuning of the metal center for enolate reactivity

The aldol reactions of tetracarbonyl(phosphine)methyl(methoxy)methylene chromium complexes and pentacarbonylmethyl (dialkylamino)methylene chromium complexes with aldehydes and ketones were examined. The reactions of the phosphine complexes give only aldol condensation products, but the desired aldol addition products can be isolated from the reactions of amino carbene complexes. This was attributed to the greater reactivity of the enolates of amino carbene complexes which is supported by a determination of the thermodynamic acidity of the dimethylamino complex 13 (pK_a=20.4). The aldol reactions of amino complexes with -chiral aldehydes occur with very high facial selectivities rivaling the best methods that have been developed for facial selectivity in the aldol reaction. The aldol reactions of amino complexes can be considered as direct synthons for amides since amide functions can be obtained in the oxidative cleavage of the aldol adducts of these complexes. As illustrative of the versatility of carbene complexes, it is also demonstrated in a photo-induced carbon-homologative demetallation, that in combination with the aldol addition reaction the unique reactions of carbene complexes provide powerful and novel overall transformations.     

Detection of C-reactive protein, streptolysin O, and anti-streptolysin O antibodies in immune complexes isolated from the sera of patients with acute rheumatic fever

Circulating immune complexes (IC) of 42 patients with acute rheumatic fever from Santiago, Chile, were studied. The complexes were isolated by polyethylene glycol precipitation and were analyzed for antibodies, antigens, and C-reactive protein. We found the complexes to be enriched in antibody to streptolysin O, particularly in the group of patients with elevated levels of IC. IgM was the predominant class of Ig present in the complexes. Western blots from 12 patients to detect antigens in the complexes showed proteins of m.w. 50,000, 60,000, and 69,000, consistent with the polypeptides of streptolysin O. Such antigens were absent in the complexes from patients with post-streptococcal glomerulonephritis and pharyngitis. Eluted antibodies from these protein bands on the nitrocellulose sheets reacted with the streptolysin O in Western blots and neutralized the hemolytic activity of streptolysin O in a microhemolysin assay. In addition, isolated complexes from several sera showed the presence of C-reactive protein bound to complexes. In vitro experiments demonstrated that [125I]C-reactive protein was not precipitated by polyethylene glycol either alone or when added to monomeric IgG, whereas it precipitated significantly when added to aggregated IgG. The detectable C-reactive protein in isolated complexes and sera samples increased after treatment with sodium dodecyl sulfate. These data suggest that circulating immune complexes in acute rheumatic fever contain streptolysin O and its antibody and raise interesting questions regarding the pathogenetic significance of C-reactive protein in the complexes.     

The electron spin resonance and absorption spectra of microsomal cytochrome P-450 and its isocyanide complexes

The absorption spectra of oxidized P-450-isocyanide complexes were the same in difference spectra irrespective of the isocyanide derivative tested. However, with these reduced P-450-isocyanide complexes, absorption at 455 mμ increased, and that at 430 mμ decreased, with increasing carbon atom number of the isocyanide derivative at a definite pH. The same changes were seen with individual complexes with increasing pH.

The dissociation constants of oxidized P-450-isocyanide complexes decreased with increase in carbon atom number of the isocyanide. These results were confirmed by electron spin resonance (ESR) spectroscopy. However, the dissociation constants of reduced P-450-isocyanide complexes were essentially identical and the dissociation constants of the oxidized and reduced P-450-isocyanide complexes were little affected by pH.

The oxidized P-450-isocyanide complexes gave magnetically specific ESR signals. The orbital energy differences of d orbitals of the heme iron of the complexes increased with increase in the carbon atom number of the isocyanide.

Purified P-450 and its isocyanide complexes were rapidly reduced by a ferredoxin-NADP⁺ reductase system.     

A Study on the Comparative Stability of Insoluble Complexes of Glucose Oxidase Obtained with Concanavalin A and Specific Polyclonal Antibodies

Summary The formation of insoluble complexes of glycoenzymes with lectins and antibodies is one of the simplest methods of enzyme immobilization. Insoluble complexes of glucose oxidase were simply obtained by mixing the enzyme with concanavalin A or a specific polyclonal antibodies solution. The concanavalin A and immunocomplexes of glucose oxidase retained more than 80% of the original enzyme activity. Expression of very high enzyme activity in insoluble complexes suggested that these aggregates were quite porous and easily accessible to substrates. Insoluble complexes of glucose oxidase showed very high stability against denaturation induced by pH, temperature, urea and water-miscible organic solvents. Complexes of glucose oxidase obtained with concanavalin A and glycosyl-specific antiglucose oxidase polyclonal antibodies were quite comparable in stability while complexes prepared using polyclonal antibodies raised against the native glucose oxidase were slightly less stable. The complexes of glucose oxidase obtained with glycosyl-specific antiglucose oxidase polyclonal antibodies showed very high stability against inactivation mediated by exposure to water-miscible organic solvents. Insoluble complexes of glucose oxidase were cross-linked with glutaraldehyde to maintain their integrity in the presence of substrates. The cross-linking of complexes resulted in a slight decrease in enzyme activity but showed a pronounced enhancement in stability against various forms of denaturation.     

Steric stabilization of poly-L-Lysine/DNA complexes by the covalent attachment of semitelechelic poly[N-(2-hydroxypropyl)methacrylamide

The concept of steric stabilization was utilized for self-assembling polyelectrolyte poly-L-lysine/DNA (pLL/DNA) complexes using covalent attachment of semitelechelic poly[N-(2-hydroxypropyl)methacrylamide] (pHPMA). We have examined the effect of coating of the complexes with pHPMA on their physicochemical stability, phagocytic uptake in vitro, and biodistribution in vivo. The coated complexes showed stability against aggregation in 0.15 M NaCl and reduced binding of albumin, chosen as a model for the study of the interactions of the complexes with plasma proteins. The presence of coating pHPMA had no effect on the morphology of the complexes as shown by transmission electron microscopy. However, results of the study of polyelectrolyte exchange reactions with heparin and pLL suggested decreased stability of the coated complexes in these types of reactions compared to uncoated pLL/DNA complexes. Coated complexes showed decreased phagocytic capture by mouse peritoneal macrophages in vitro. Decreased phagocytosis in vitro, however, did not correlate with results of in vivo study in mice showing no reduction in the liver uptake and no increase in the circulation times in the blood. We propose that the rapid plasma elimination of coated pLL/DNA complexes is a result of binding serum proteins and also of their low stability toward polyelectrolyte exchange reactions as a consequence of their equilibrium nature.     

Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.     

Adhesion of colloidal polyelectrolyte complexes to wet cellulose

The adhesion of wet regenerated cellulose to colloidal complexes formed between carboxymethyl cellulose (CMC) and polyvinylamine (PVAm) was evaluated by measuring the force to delaminate pairs of regenerated cellulose membranes bound together with polyelectrolyte complex. The most important parameter was the surface composition of the colloidal complex particles. High delamination forces corresponded to using complexes coated with excess PVAm whereas low adhesion was observed for both CMC coated complexes and complexes in which the PVAm was replaced with polymer bearing quaternary amine groups. Adhesion with complexes was highest at pH 4 and rather insensitive to pH from 6 to 9. Finally, mild TEMPO/NaBr/NaClO oxidation of the cellulose gave much stronger adhesion when PVAm was in excess but not with the CMC rich complexes.     

Complexing properties of some pyrimidines

The synthesis of transition metal barbiturate, and thiobarbiturate complexes containing different functional groups of variable electronic character with CoII, NiII, CuII, PdII, and PtII have been prepared. The stereochemistry and the mode of bonding of the complexes were determined by elemental analysis and electronic and vibrational spectra together with their magnetic moment values. Electronic spin resonance of copper complexes were recorded. The Racah parameter of some cobalt and nickel complexes were calculated. Some of the complexes are of mixed stereochemistry. All the PdII or PtII complexes are of square planar geometries.     

Microcalorimetric studies of the effects of platinum group metal complexes on bacterial growth

A range of platinum group metal complexes (PGMC) were screened for antibacterial activity against Klebsiella aerogenes and Staphylococcus aureus. The effects of the complexes were monitored by changes in the thermal and growth properties of the organisms. Active complexes caused an immediate cessation of power and biomass production which did not recover whilst the complex was present in the medium. Removal of the complex by washing the cells allowed the growth of the small viable proportion of the cells; the majority of the cells had been killed. Changes which occurred in aqueous solutions of active complexes rendered them less bactericidal; this was a possible cause of regrowth observed at sub-bactericidal levels of some complexes. Resistance to active complexes could not be achieved by serial subculture. Three palladium complexes active against K. aerogenes all had similar square planar structures, but in general it was not possible to correlate activity with structure. The unique effects of the PGMCs at low concentrations, combined with the apparent inability of the bacteria to develop resistance to them, makes the complexes a valuable addition to the antibacterial arsenal.     

Lung injury produced by immune complexes of varying composition

Immune complexes consisting of rabbit antibody to bovine serum albumin (BSA) have been made up at 1X, 3X, 6X, 8X, and 20X antigen equivalence. The complement fixing activity of these complexes is inversely proportional to the amount of antigen present in the complexes, and, as expected, solubility of the complexes progressively increases with increasing amounts of antigen. The ability of these complexes to induce acute pulmonary injury and inflammatory responses has been quantitatively assessed. Complexes preformed at antigen equivalence are the most damaging to lung, correlating with their complement fixing activity. When the antigen concentration in the complexes is increased 3 to 6 times beyond the point of equivalence, the phlogistic activity of the complexes drops off rapidly, as demonstrated by a sharp decline in the changes in vascular permeability, hemorrhage, and morphologic evidence of inflammation. These studies provide the first evidence that changing the physicochemical parameters of preformed immune complexes by simply altering the ratio of antigen to antibody can dramatically alter the phlogistic properties of immune complexes for pulmonary tissue.     

Interaction of platinum and palladium 5-sulfo-8-mercaptoquinoline complexes with sarcoplasmic reticulum Ca2+-dependent ATPase]

5-Sulfo-8-mercaptoquinoline complexes of platinum and palladium (complexes I and II) effectively inhibit Ca2+-dependent ATPase from sarcoplasmic reticulum. However, in contrast to K2PtCl4, K2PdCl4 and other previously investigated platinum and palladium complexes, they do not interact with the thiol groups of the enzyme. The inhibiting effects of complexes I and II are reversible and competitive with respect to ATP. In aqueous solutions complexes I and II decrease the fluorescence of tryptophane with a simultaneous shift in fluorescence towards the long-wave region. The same effect is exerted by the complexes on the fluorescence of tryptophane residues in Ca2+-dependent ATPase preparations. An addition of tryptophane to the enzyme preparations preincubated with complexes I and II partly restores the enzyme activity. It is assumed that the inhibiting effect of complexes I and II is due to their non-covalent interactions with the trytophane residues vicinal to the ATPase center.     

2-Oxoacid dehydrogenase complexes of Escherichia coli: cellular amounts and patterns of synthesis.

The oxidative decarboxylations of pyruvate and 2-oxoglutarate in Escherichia coli are carried out by two large, multienzyme complexes: pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. The enzyme complexes each contain three subunits: two are unique to the individual complexes, the third is shared between them. Resolution of the polypeptide subunits on two-dimensional gels allowed quantitative analysis of their cellular levels and patterns of synthesis in growing cells. Cells growing in glucose-salts medium were found to contain roughly 85 to 136 pyruvate dehydrogenase complexes and 73 2-oxoglutarate complexes. Lipoamide dehydrogenase, the subunit shared by the two complexes, was found to be in significant excess of its stoichiometric demand in the two enzyme complexes under most growth conditions. The subunits unique to each of the complexes were coordinately regulated over a wide variety of growth conditions and a broad range of expression. The two complexes responded to different, but partially overlapping, regulatory signals. Most importantly, the shared subunit was actively regulated to accommodate its demand in both enzymes. These results are discussed with regard to possible mechanisms of regulation of the enzyme complexes in general and of the shared subunit specifically.     

A molecular mechanics investigation of the structures and energetics of two classes of Ru(II) complexes with applications in homogeneous catalysis

We have used the extensible systematic forcefield (ESFF) to model two classes of chiral organometallic complexes with Ru(II) centres, both complexes having been shown to have excellent catalytic performance with respect to asymmetric ketone hydrogenation. Our results compare favourably with all available experimental data for these complexes, illustrating that the ESFF can be applied successfully to these systems. The results we obtain are useful and relevant in connection with the study of these complexes as catalysts and in turn the results support the further use of the ESFF for modelling other organometallic complexes.     

Combinatorial semisynthesis of biomarker-IgM complexes

Circulating immune complexes formed by tumor antigens and immunoglobulin M (IgM) represent a novel class of biomarkers with diagnostic value for early cancer detection. The quantitative analysis of these immune complexes is achieved by enzyme-linked immunosorbent assay (ELISA) methods using a purified calibrator from samples of patients with cancer. These complexes obtained from samples of human origin are not suitable for cost-effective production processes with high safety standards. Given the ill-defined biomarker/IgM ratio in these complexes, semisynthesis with retention of functional properties is difficult to achieve and may vary widely according to the batch-to-batch heterogeneity of starting biological preparations. Here the authors describe the development of a combinatorial method for defining the optimal reaction conditions for the reproducible semisynthesis of biomarker-IgM complexes by exploiting the biotin-avidin technology. The method relies on screening by ELISA the 3D composition space defined by the combinatorial variation of biotinylated-biomarker, biotinylated-IgM, and avidin concentrations aiming to select those conditions leading to biomarker-IgM complexes with the highest immunoreactivity. The method allows the reproducible synthesis of species with immunoreactivity comparable to that of natural immune complexes and endowed with sufficient stability to be used as calibrators in ELISA.     

Inactivation of myoglobin by ortho-substituted arylhydrazines. Formation of prosthetic heme aryl-iron but not N-aryl adducts

Stable phenyl-iron complexes are known to form in the reactions of myoglobin, hemoglobin, and catalase with phenylhydrazine. The phenyl moiety in these complexes migrates from the iron to a nitrogen of the porphyrin upon denaturation of the hemoproteins. Complexes obtained from myoglobin and ortho-substituted phenylhydrazines, however, are much less stable, have distinct chromophores, and do not yield N-arylporphyrins. These abnormal properties imply that the complexes differ in structure (e.g., they are aryldiazenyl-rather than aryl-iron complexes) or that ortho substitution strongly alters the chemistry of aryl-iron complexes. The present NMR studies unambiguously demonstrate that ortho-substituted phenylhydrazines give normal aryl-iron complexes but that the aryl group in these complexes is conformationally locked and is unable to shift from iron to nitrogen.     

Inhibition of recA-mediated strand exchange by adducts of azacytosine-containing DNA and the EcoRII methylase

Wild type Escherichia coli cells containing elevated levels of DNA (cytosine-5)methyltransferases have increased sensitivity to the toxic effects of 5-azacytidine. The methyltransferases form tight binding complexes with azacytosine in DNA which could interfere with the recA recBCD repair pathway which is largely responsible for cell survival after treatment with the drug. We therefore determined if these complexes interfered with recA-mediated strand exchange in vitro. 32P-Labeled DNA fragments containing a single EcoRII site, with cytosine in the (-) strand replaced by 5-azacytosine, were prepared. We investigated the effect of the EcoRII methyltransferase on recA-mediated strand exchange with homologous M13 DNA by electrophoresis in agarose gels. In the absence of the methylase the rate and extent of strand exchange of azacytosine-containing DNA is the same as control DNA. In the presence of the methyltransferase strand exchange is inhibited, but some incorporation of duplexes into recA-single-stranded DNA (ssDNA) complexes still occurs. The formation of these complexes is dependent on the length of the fragment 3' to the methylase binding site on the strand complementary to the ssDNA. The greater the length the greater the number of complexes that form. S-Adenosyl-L-methionine, which enhances binding of the methyltransferase to azacytosine-containing DNA, causes an increase in the inhibition of strand exchange and an increase in the number of inactive complexes formed. The complexes can be dissociated with guanidinium chloride which denatures the methyltransferase and leads to release of the (+) strand. The (-) strand remains associated with the ssDNA. This result implies that a plectonemic joint is formed between recA-ssDNA complexes and azacytosine-containing DNA-methyltransferase complexes. However, branch migration in these complexes is inhibited. Denaturation of the methyltransferase allows branch migration to proceed to completion, releasing the (+) strand.     

Co-operative binding of the globular domain of histone H5 to DNA.

The globular domain of histone H5 (GH5) was prepared by trypsin digestion of H5 that was extracted from chicken erythrocyte nuclei with NaCl. Electron microscopy, sucrose gradient centrifugation, native agarose gel electrophoresis and equilibrium density gradient ultracentrifugation show that GH5 binds co-operatively to double-stranded DNA. The electron microscopic images suggest that the GH5-DNA complexes are very similar in structure to co-operative complexes of intact histone H1 (or its variants) with double-stranded DNA, studied previously, which have been proposed to consist of two parallel DNA double helices sandwiching a polymer of the protein. For complexes with GH5 or with intact H1, naked DNA co-sediments with the protein-DNA complexes through sucrose gradients, and DNA also appears to protrude from the ends and sides of the complexes; measurements of the protein-DNA stoichiometry in fractionated samples may not reflect the stoichiometry in the complexes. An estimate of the stoichiometry obtained from the buoyant density of fixed GH5-DNA complexes in CsCl suggests that sufficient GH5 is present in the complexes for the GH5s to be in direct contact, as required by a simple molecular mechanism for the co-operative binding. Chemical crosslinking demonstrates that GH5s are in close proximity in the complexes. In the absence of DNA, GH5-GH5 interactions are weak or non-existent.     

Binding characteristics of dimeric IgG subclass complexes to human neutrophils

Immune complexes were prepared by incubation of human IgG paraproteins with F(ab')2 fragments of the mAb K35 against the kappa-L chain of human IgG. The composition of these complexes was analyzed by centrifugation over sucrose gradients, by gel filtration, by RIA with either IgG Sepharose or K35 Sepharose and by double-labeling studies. The results indicated that the complexes consist of saturated tetramers composed of two IgG molecules cross-linked by two F(ab')2 fragments of the mAb. These complexes were used to study the binding of the different IgG subclasses to human neutrophils at 4 degrees C. Human neutrophils bound IgG3 complexes approximately three times faster than IgG1 complexes. Binding of IgG2 or IgG4 dimers to the neutrophils was undetectable. The same number of IgG1 complexes and IgG3 complexes bound to the neutrophils, but considerable inter-donor variation was found (mean number of Fc gamma R per neutrophil: 190,000, range 120,000 to 400,000). The Ka for the binding of IgG1 complexes to neutrophils (median 11 x 10(7) M-1) was lower than the Ka for the binding of IgG3 complexes (median 47 x 10(7) M-1). Competition studies between labeled IgG1 complexes or IgG3 complexes and unlabeled complexes showed that the Fc gamma R of human neutrophils do not display an IgG subclass specificity. Incubation of neutrophils with a mAb against the FcRIII completely blocked the binding of IgG1 complexes and IgG3 complexes. Incubation with a mAb against the FcRII reduced the affinity of the complexes for the neutrophils but had no effect on the maximum number of complexes bound. This indicates that one complex may bind simultaneously to one FcRIII and to one FcRII.